1. Field of the Invention
This invention relates to a melt treatment apparatus for melting, with use of a plasma torch, a wide variety of general wastes containing inorganic matter, metal or organic matter, sewages, municipal solid wastes, ashes resulting from incineration thereof, atomic radioactive wastes of a low level and the like.
2. Description of the Related Art
A variety of general wastes containing inorganic matter, metal or organic matter, sewages, municipal solid wastes and ashes derived by incinerating the same have heretofore been disposed of as landfills in designated locations. However, because of limited space of these locations and also limited space and period for storage, a growing demand has of lately been voiced for a technique of reducing the volume of each such waste. To this end, a need exists for the development of a melt solidification method in which the waste is treated to have decreased volume and heated at a temperature of higher than the melting point thereof, followed by solidification of the melt by cooling. On the other hand, melt furnaces in common use have been designed to melt the waste by combustion of a fossil fuel chosen from kerosine, heavy oil or other hydrocarbon gas fuels. This combustion type of melt solidification, however, involves restricted combustion temperature and hence makes it difficult to subject higher-melting wastes to melt solidification.
A plasma type of heating, by contrast, can evolve a gaseous body of temperatures up to several tens of thousand centigrades through excitation of electricity, thus enabling easy heating of wastes at temperatures above their melting points. A melt treatment apparatus designed to employ such plasma heating technique is constructed basically with a melt furnace and a plasma torch mounted thereon in such a manner that a material (a waste or the like) to be heated is caused to melt by means of a plasma arc jetted out of the tip of the plasma torch.
A melt treatment apparatus is known in which by the use of a melt furnace provided with the above plasma torch, a melt is treated in a batchwise manner (see Japanese Patent Publication No. 6-94927). As seen in FIG. 13A through FIG. 13D of the accompanying drawings, a melt treatment apparatus 91 is comprised of a melt furnace 97, a furnace cover 92 and a furnace chamber 93. A plasma torch (not shown) is freely slantingly attached to the cover 92 for heating a material to be treated. A truck 96 is secured to the chamber 93 such that the latter is transported to a melt outlet where the melt is discharged. The truck 96 is provided with lifting and slanting members 94, 95 for tilting the chamber 93 in place at the melt outlet. Moreover, the melt treatment apparatus 91 has a pair of parallel rails (not shown) installed on which the truck 96 is allowed to run so as to convey the chamber 93 to the melt outlet.
The melt treatment apparatus 91 thus assembled allows the material to be heated to be molten by means of the plasma torch (not shown) as illustrated in FIG. 13A and subsequently separates the cover 92 from the chamber 93 by the action of the lifting and slanting members 94, 95 secured to the truck 96 as seen in FIG. 13B. The chamber 93 is transported to the melt outlet by the travel of the truck 96 as illustrated in FIG. 13C, and the melt is taken out with the chamber 93 tilted by the action of the lifting and slanting members 94, 95 as seen in FIG. 13D.
Further reference to FIG. 14B shows a melt furnace 102 constituted of a melt treatment apparatus 101 which has a plasma torch 103 freely slantingly disposed (see Japanese Patent Publication No. 59-116199). As has been made clear from FIG. 14A, the furnace 102 is provided at a side portion thereof with a melt outlet 105 for discharging a hot melt 106, from which melt discharge passages 107 are caused to extend for discharging the melt 106. Disposed below the melt outlet 105 are those pipes 108, 109 used to flow cooling water in order to cool and solidify the melt 106.
The melt treatment apparatus 101 discussed above is intended to melt, by means of a plasma torch, a material to be heated. Yet the melt 106 located adjacent to the inner wall of the melt furnace 102 is cooled and solidified through cooling water supplied through the pipes 108, 109 with the consequence that a dam is formed. This dam is thereafter heated to molten with use of the plasma torch 103 so that the melt 106 is caused to flow. Thus, the melt treatment apparatus 101 performs controlled flow of the melt 106 in a batchwise fashion.
The melt treatment apparatus 91 illustrated in FIGS. 13A to 13D, however, is structured in such a manner that the cover 92 is separated from the chamber 93 and also, that the chamber 93 is conveyed to the melt outlet with the aid of the truck 96. This known apparatus has the drawback that it calls for complex machinery and equipment and hence results in increased floorspace and added cost.
Additionally, the melt treatment apparatus 101 shown in FIG. 14 is contrived to cool and solidify a melt through a cooling water to thereby form a dam. When the cooling water is allowed to pass below the dam (below the melt outlet 105) as seen here, the pipes 108, 109 for running of the cooling water also become heated upon heating of the dam with use of the plasma torch 103. In this instance, where a sufficient amount of cooling water fails to run through the pipes 108, 109, the heat arising from above the dam dominantly affects such pipes, thus doing damage to the pipes or causing a hazardous explosion in the pipes of steam, namely water vapor. Furthermore, since the cooling water produces only a stationary magnitude of cooling capability, the resultant dam would in some cases get destructed depending upon varying heating conditions (a cold solid body would become molten at an area in proximity to the melt output). This has the problem that controlled discharging of the melt is not reliably attainable.